Published January 15, 2011

The Institute of Agriculture at San Michele All’Adige looks for ways that orchardists and vineyardists can farm more efficiently and reduce labor needs. Following an intensive thinning study by the institute, more than 40 mechanical thinners are now in operation in Italian orchards. But their latest focus is ­trying to design an orchard system that could be completely mechanized.

It takes an annual average of 240 hours per acre to produce apples in the South Tyrol province of Trentino, according to Alberto Dorigoni of the research institute and school at San Michele. The 240 number includes the use of orchard platforms.

Platforms, commonly used in Italian orchards, have significantly reduced labor costs by eliminating the need to lug tall ladders around to open and close hail nets and pick fruit. One platform covers about 25 acres, Dorigoni said. Depending on variety, platforms can double the picking efficiency during harvest. An average worker on a ladder picks about 330 pounds of apples per hour compared to a platform worker picking 440 to 660 pounds per hour.

“Of course, they help a lot,” Dorigoni said of platforms. Platforms can be useful on a family farm when operated by the owner, but he added that they can lose some of their productiveness (as with any piece of equipment) when operated by seasonal workers instead of owners. Usually, less than half of the apples are picked from the platform, with most of the fruit picked from the ground. “Platforms are useful, but you can do more when you’re on your feet. One of the goals we have in mind is to get rid of platforms so that we could achieve a pedestrian orchard.”

An intensive, four-year study of mechanical thinners involving more than 30 trials shows mostly satisfactory results, Dorigoni said. Mechanical thinners are more consistent than chemical thinning agents and are not influenced by weather and temperatures. Mechanical thinners have worked in achieving return bloom on alternate-bearing varieties. For Fuji, a variety that doesn’t always respond well to chemical thinners, they’ve had good results in reducing fruit set while improving fruit size and achieving return bloom.

“Mechanical thinners can easily be combined with chemical thinning,” he said, adding that in trials they almost always saw improved results from the combination of the two when heavy thinning was needed. The researchers at San Michele have found that the ideal time to mechanically thin is right before bloom.

Through the years, the number of strings on the German-made Darwin machine has been reduced, he said, which has improved the capabilities of the machine.

In some of their trials, less than 2 percent of fruit have been misshapened from the mechanical thinner. Last year, less than 5 fruit per 1,000 showed any damage. He notes that chemical thinners can sometimes result in pygmy fruit, but that doesn’t happen with mechanical thinners.

In outlining the drawbacks to mechanical thinners, he said there is risk of a late frost further reducing fruit set after mechanical thinning has taken place. Trees must have a slender canopy, and mechanical thinners are not selective in terms of the king bloom. Some temporary damage to vegetation will occur.

Dorigoni identified the following varieties to be compatible with mechanical thinning: Red Delicious, Fuji, Golden Delicious, and Gala. Braeburn and Pink Lady are not as suitable because they respond to chemical thinners and/or do not usually need ­thinning.

The San Michele studies have shown that mechanical thinning can reduce labor for hand thinning and chemical application by 20 hours per acre for most varieties, he said. “For varieties that are difficult to thin, it’s common to spend up to 150 hours per hectare [60 hours per acre] for hand labor and chemical thinning. A good mechanical thinner can save more than 50 hours and I think closer to 100 hours in some varieties.”

Fruiting wall

Dorigoni believes the future of orchard systems in Italy may well be something that looks like a fruiting wall and utilizes biaxis trees. A fruiting wall would allow mechanical thinners and pruners to be used, improve mechanical and chemical weed control under the tree row, and the bottom of the tree would still receive good sunlight, a factor that can be an issue with spindle-shaped trees. “That’s why we’re looking at the biaxis system.”

In Italy, biaxis or double leader trees are trademarked as the Bibaum tree. Developed ten years ago by an Italian nursery, Bibaum is a German term for two trees. The divided tree has twice the number of leaves, and branches are naturally short.

He’s found double-axis trees to be 20 to 30 percent more productive than spindle systems because fruit are distributed more uniformly, he said. “We have measured the crop in different growing areas on the tree, and there are differences between a biaxis and spindle,” he said.

When looking at the crop on different layers in the tree, they found that in the top third of the tree, there were no color and quality differences between the spindle and double-axis. “But if you go down half or lower in the tree, you lose color in the spindle.”

Pruning

A fruiting wall would facilitate a simplified mechanical pruning concept developed by French researchers that involves pruning in late spring when the trees have 12 to 14 leaves per shoot. He said they are studying the use of mechanical pruning right after harvest, with a follow-up in June of the next year.

“The goal of mechanical pruning is not to substitute [replace] hand pruning, but to reduce the number of hours needed for pruning,” Dorigoni said. “We need to reduce pruning by 50 to 100 hours of hand work in the winter.”

Dorigoni hasn’t studied total labor hours in a fruiting wall compared with a spindle system, but he said the French have found the fruiting wall to be 10 percent more efficient than other orchard systems. “There is less tree training or limb bending and tying involved in the second and third year of the orchard, saving another 100 labor hours with the double-axis trees because no bending is necessary.”

When the mechanization steps are combined, it adds up, he said. “All of these things put together, it adds up to significant labor savings.”